1. Field of the Invention
The present invention relates generally to screwdrivers, and in particular to methods, devices and systems for adaptively driving screws using a screw driving tool.
2. Description of the Related Art
Automated screwdriver systems have been employed in the mass production of various devices, such as a disk drive comprising a head stack assembly (HSA) that is fastened to a base, and a cover also fastened to the base, typically by means of screws. Conventionally, the screw driving process includes driving the screw at a first low speed while monitoring the torque developed on the screw by the bit of the screw driver. The screw is driven (rotated) at that first low speed until a predetermined percentage (for example, 65%) of a target torque value is reached. Thereafter, the screw is driven at a second, even lower, speed until the target torque is reached. This screw driving approach has several disadvantages associated therewith, including finding the first thread of the hole into which the screw is to be driven, material/tool variations and the low yield of the screw driving tool (the number of screws it is able to drive within a predetermined period of time).
In particular, material variations (e.g., thickness of the material and depth and threading of the hole) from one part to another may introduce variations that may not be well controlled while driving the screw. Similarly, tool variations from one tool to another (e.g., tolerances in the screw driving tool) make measurements from one tool unreliable for controlling the operation of another tool. Driving the screw at the first low speed while monitoring torque and thereafter lowering the speed of the screw driving even further as the target torque is approached, significantly decreases the throughput of the screw driving systems.
There is, therefore, a need for a screwdriver for driving screws into workpieces that may improve throughput by accounting for such material/tool variations.